This invention relates to apparatus for inducing nuclear magnetic resonance in a flowing medium.
Nuclear spin resonance, more commonly known as nuclear magnetic resonance (NMR), measurements of flowing mediums have been used to establish flow velocity, or mass throughput, and there is particular interest in the application of such a method to the instance of unsteady high-speed two-phase flow in wide tubes, such as occurs for example in the circulatory cooling systems of nuclear reactors. An NMR signal is obtained by examining the radio frequency spectrum of a sample in a strong magnetic field. The magnetic field causes nuclear spin splitting, the "resonance" being the resulting transition frequency between the split energy levels. Previously, systems have been proposed in which separate magnets have been used for the production of polarising and measuring fields, and a modified system in which a single magnet is used for the two fields. Two major considerations in designing apparatus of this type are establishing the best possible signal to noise ratio, and simultaneously keeping the assembly compact and the weight to a minimum.